Begin scouting first generation Bean Leaf Beetles one week after the
predicted peak emergence of the 1st generation to determine control
strategies for the 2nd generation (next month). Peak 1st generation
emergence will occur around 1212 GDD’s following soybean emergence.

ISU
has developed a control strategy (for 2nd generation beetles
in Mid-August and September) based on 1st generation population numbers. Based upon a high density
of first generation beetles, it is expected that the second generation will
exceed the economic threshold. This new management concept stops the
second-generation beetles long before they reach the old economic threshold.

The first thing to do is determine the date soybeans emerged, then refer to
the accumulated GDD graph and match dates. Begin sampling fields 1 week after
peak emergence. If the sample is below threshold (Table 1), scout again the next week.
If the sample is still below threshold, scout 1 more week. If 1st generation
beetles are above threshold, scout again mid August to confirm beetles are
present, then spray.

Notice: This is scouting of 1st generation beetles to determine
control of 2nd generation beetles.

Figure 1. Degree Day Accumulation for predicting emergence of 1st Generation BLB based on
emergence date of the soybean field.

Degree-Day Data as of July 11, 2005

Figure 2. Overwintered, First and Second generation bean leaf beetle
estimated population cycle.